The present invention generally relates to securing layers of differing density sponge material together to form a composite body and mechanically treating the composite sponge body so that it will form a specific shape upon hydration.
There currently is a need to provide medical devices which can be inserted into the human body in one condition and when hydrated by body fluids change their shape into a desired shape or form, pushing an organ or tissue to a different position, or providing a protective shield for the organ or tissue to protect the same during surgery or treatment.
It is often necessary during surgery to displace or temporarily relocate tissue or organs from their natural anatomical position. This is done to facilitate surgery at the site. Organs and tissue must be handled gently to prevent damage or to minimize the tendency to produce adhesions, post operatively.
Many devices have been developed to address this problem: tapes, metal retractors of various designs and fabric sponges have all been used. These are all functional but have various deficiencies.
Tapes are useful for displacing small organs such as veins and arteries. They have tendency to cut through the organ when pulled to adjust the position of the organ because of their linear contact with the organ.
Metal or plastic retractors have proven to be useful. They can hold large organs or pedicles of tissue, even when put under considerable tension. However, the metal surface and the high degree of compression within the jaws of the retractor tends to create necrosis of the tissue.
Fabric sponges are also very useful for packing cavities and tissue adjacent to the organ to be protected. They are conformable to the space available, are soft and to some degree absorbent. The fabric sponges suffer from the need to use large quantities of sponge to get sufficient mass to displace tissue and from being weak and easily frayed creating a risk of leaving filaments behind. Such filaments will be treated by the body as foreign matter and could become a nexus for infection or create granuloma.
While medical sponges are generally used to absorb bodily fluids as blood, serum, spinal fluid, tissue fluid, urine, sweat, bile, digestive juices and other fluids, they are also used to displace organs or tissues and dam and hold organs and tissues. See for example U. S. Pat. No. 4,533,356 directed toward an absorbent rod shaped device used to keep organs in a given position; U.S. Pat. No. 4,889,107 directed toward a surgical dam constructed of an open celled plastic foam having a metal core allowing it to be bent into a desired configuration and U.S. Pat. No. 3,961,629; a surgical sponge pad having a surfactant coating to accelerate absorption of body fluids into the sponge pad.
A number of other patents are known which show various devices Which have been designed to change shape to provide a desired medical function or to impart a mechanical force for accomplishing a desired result.
In this area, U.S. Pat. No. 5,149,332 discloses an absorbent product which is longitudinally compressed or microcreped to produce microroundulations by compressing the web in its own plane in the direction of its length with compressive forces exerted substantially parallel to a longitudinal direction of the material. The product when compressed has at least 10 microroundulations per inch in the layer in the direction of treatment. The microroundulated layer is shape-retentive and has stored mechanical energy capable under an activating condition such as hydration to cause the product to expand. The product is envisioned to be used as superabsorbent assemblages, menstrual tampons, pads such as bandages, compresses, rolls and the like and liquid distributing articles.
A number of shaped polymeric compositions for surgical use which can absorb liquid and thereby expand or contract in one direction are shown by U.S. Pat. No. 4,565,722. Examples of such different shaped memory devices are shown in the figures of the patent, the even numbers representing expanded devices. One shaped memory device is a triangular shaped endodontic point for insertion into a tooth after a nerve cavity has been removed. The axial length stays unchanged while the product swells radially. Another shaped memory device is initially in the form of a sheath and expands radially for holding severed nerve ends, veins or arteries in close proximity so that the contracted ends of the sheath provide a soft and pliable grip on the nerve, vein or artery ends. Another shaped device is shown which swells in contact with body fluid to a dumbbell shape which can be used for providing a permanent but non-irritant Fallopian tube closure. Still another shaped memory device is directed to a cylindrical blank which expands in diameter. Another shaped memory device expands in thickness only provided that d.sub.1 d.sub.2 equals the linear expansion ratio of the material during hydration to give the expanded insert an arcuate outer surface for use as a breast implant.
U.S. Pat. No. 4,159,719 discloses a dehydrated wick of tightly coiled cellular sponge like material which when hydrated uncurls and expands radially to snugly engage the inner peripheral wall of the ear canal. Likewise U.S. Pat. No. 4,034,759 discloses a moisture expandable prosthesis constructed of a hollow cylindrical wick of dehydrated regenerated cellulose sponge material. The sponge material is tightly compressed so that it is rigid for insertion endwise into a body opening. When the wick is moistened, it expands radially to engage the inner peripheral walls of the opening and when used in association with an ear canal, provides an axial opening through which the expanded member permits sound waves to reach the ear
U.S. Pat. No. 4,979,947 discloses a resilient foam material collapsed into a small volume condition having a string or cord passing through the material which when introduced into an orifice absorbs moisture to expand at a predetermined size and shape for blockage. Traction on the string during withdrawal results in compression of the contained foam cube allowing comfortable withdrawal from the body orifice.
A multi-layered tampon formed by folding over a single layer of absorbent batt is disclosed by U.S. Patent Number 4,327,728. Pockets containing hydrocolloid and introfying particles are placed so as to lie between the layers and project into each layer. The dry solid granules of hydrocolloid particles when wetted begin to swell expanding the pockets. As the pockets expand, the expanding walls push the adjacent fibers of the batt aside while keeping the hydrocolloid particles trapped within the pockets thus significantly increasing the total absorptive capacity of the structure.
U.S. Pat. No. 4,019,498 discloses a vaginal device for urinary incontinence in the form of a cellular mushroom-shaped body which is precompressed and inserted in a plastic sleeve. After insertion into the vagina the sleeve is pierced allowing the introduction of air into the sponge-like cells of the device permitting it to expand and exert pressure on the urethra.
Because sponge material is difficult to place in human body Cavities after it has absorbed fluid and obtain the desired results and since pre-wetting may decrease the amount of fluid that can be adsorbed, some absorbent sponges and dressings are placed in human body cavities in a dry compressed form. The present invention takes this prior art one step further and provides a layered different density sponge material which when placed in the human body cavity absorbs fluid to expand into another shape due to the different expansion capacities and equilibrium water concentration of the different density sponge materials.